It is now part of the normal constraints. Added a special
workaround for functions, since otherwise the output is a
bit redundant and quite confusing.
Also, constraints are now processed in order of complexity.
This does not affect type safety. It uses a bit more CPU.
But it makes the output that much easier to read.
Also, removes the weird FunctionInstance hack. Instead,
the more industry standard way of annotation the types
on the function call is used. As always, this requires some
hackyness for Subscriptable.
Also, adds a few comments to the type unification to help
with debugging.
Also, prints out the new constraints that are received.
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